Application of natural feed additives to enhance growth performance, innate immunity, gut microbiome, and disease resistance of Nile tilapia (Oreochromis niloticus) raised in biofloc and recirculating clear water systems

Abstract

With global demand for animal protein growing, aquaculture has shifted toward more intensive production. However, intensified systems are often challenged by disease outbreaks and water quality issues. Biofloc technology improves water quality through microbial activity and can reduce feed costs and wastewater discharge, while functional feed additives offer promising alternatives to antibiotics. The first part of this project evaluated the effects of dietary supplementation with humic acid (HA) and fulvic acid (FA) in Nile tilapia (Oreochromis niloticus) reared in a biofloc system. Fish fed HA showed improved growth performance, and both HA and FA increased gut microbial diversity and altered community structure. A second trial assessed graded inclusion levels of a commercial phytogenic additive in tilapia challenged with Streptococcus agalactiae and Flavobacterium oreochromis. Growth performance was unaffected, but the highest inclusion level improved survival following F. oreochromis challenge. These findings support the use of functional feed additives as practical alternatives to antibiotics in tilapia culture.